1. Field of the Invention
This invention relates to portable power tools, and more particularly to attachments for existing portable power supplies which increase the versatility thereof.
2. Description of the Prior Art
Portable power tools presently manufactured and marketed normally include a light weight but powerful power source, such as a gasoline engine, in combination with a single purpose tool. Power tools such as chain saws, cut-off saws, disc grinders, weed cutters, buffers and polishers, brush cutters, and emergency water pumps are well known. It is prohibitively expensive for a person with an infrequent need for a particular power tool to stock his shop with a complete list of equipment.
To increase the versatility of single purpose power tools, special adaptations have been made to many tools. Modifications to chain saws are especially desirable, because the modern chain saw gasoline engine is well developed and combines light weight with high power. U.S. Pat. No. 2,810,409 shows a rotary cutter attachment for a chain saw which is useful for clearing brush and undergrowth. Although the attachment of the U.S. Pat. No. 2,810,409 patent increases the versatility of a conventional chain saw, it is apparent that the chain saw is nevertheless limited to only one additional use. Further, there is no positive means for locating the attachment relative to the chain saw engine for applying and maintaining proper belt tension.
U.S. Pat. No. 3,382,898 shows a spring loaded mechanism for setting and maintaining a desired chain tension during operation of a chain saw. The chain bar is reciprocalable under the action of the spring because a longitudinally adjustable spacer thicker than the chain bar is interposed between the bar mounting nut and the chain saw engine cover plate. The chain tensioning device of the U.S. Pat. No. 3,382,898 patent is not of a positive type in either the axial or transverse directions of the chain bar. Consequently, the chain bar is susceptible to vibrations along two axes during operation. Further, the chain saw is useable only for the usual sawing operations.
U.S. Pat. No. 3,533,456 discloses a brush cutter attachment for a chain saw which has an elongated mounting member having its axis coincident with the axis of the chain saw engine output sprocket. It is apparent that replacing the chain saw chain bar with the attachment of the U.S. Pat. No. 3,533,456 patent is a time-consuming procedure, because several chain saw parts must be removed. Additionally, the attachment is useful for only limited purposes.
U.S. Pat. No. 3,580,342 shows an impact wrench attachment for a chain saw. The attachment is of limited use. Moreover, there is no positive means for applying and maintaining tension to the driving chain.
U.S. Pat. No. 4,382,334 shows a cassette type chain saw having a chain tensioning mechanism in the form of a threaded device acting between the chain saw housing and the cassette. While the mechanism does provide positive chain tension and control, it requires an engine housing and cassette designed specifically for each other and is not adaptable to chain saws without the cassette feature. Moreover, the saw of the U.S. Pat. No. 4,382,334 patent is limited to the usual chain saw cutting operations.
Thus, a need exists for apparatus which converts a conventional chain saw into a variety of power driven tools in a convenient and safe manner.